Carburetor

ABSTRACT

A carburetor so constructed that a portion of a temperature detector which is displaced by a temperature change of an engine is mechanically connected to a fast idle cam by means of a cable to control the degree of opening of a choke valve by said cam and further the displacement of said fast idle cam is transmitted to a throttle valve through a link work, whereby the degree of opening of the throttle valve is automatically controlled according to the degree of opening of the choke valve without actuating an accelerator pedal.

United States Patent Suda et al. 451 A 30, 1974 CARBURETOR 3,151,1899/1964 McSeveny 261/39 A 3,575,389 4/1971 Goto et al 261/39 A [75]Inventors: Tosh! Suda, Nagoya H1sanor1 2 774 343 5 1973 S h ff t I 26139 1 A Kobayashi, Chita, both of Japan c a are a l [73} Assignee:Nippondenso Co., Ltd., Kariya-shi, r mary Examiner-Tim R. MilesAichi-ken, Japan Attorney, Agent, or FirmCushman, Darby & 22 Filed:Sept. 21, 1971 Cushma [21] App]. No.2 182,413 57 ABSTRACT A carburetorso constructed that a portion of a tem- [30] Foreign ApplicationPriority Data perature detector which is displaced by a temperatureSept. 24, 1970 Japan 45-94773 change of an ngin is m hanic lly connectedto a fast idle cam by means of a cable to control the degree 52 us. (:1.261/39 A, 261/52 of opening of a choke valve y said cam and further [51]Int. Cl. F02m l/l0 h pl men f ai fast idle cam is transmitted to [58]Field of Search 261/39 A, 52 a throttle valve gh a link work, whereby hgree of opening of the throttle valve is automatically [56] ReferencesCited controlled according to the degree of opening of the UNITED STATESPATENTS choke valve without actuating an accelerator pedal.

2,810,559 10/1957 Winkler 1. 261/39 A 1 Claim, 4 Drawing FiguresCARBURETOR BACKGROUND OF THE INVENTION This invention relates generallyto a carburetor and particularly to a carburetor comprising an automaticchoke mechanism.

Conventional carburetors of this type comprise temperature detectingmeans consisting of a bimetal and are so constructed that a choke valveis operated according to engine temperature by said bimetal which isactuated by the temperature of the exhaust gas or cooling water of theengine, whereby a suitable concentration of fuel-air mixture isobtained. However, while the engine temperature, e.g., the cooling watertemperature, is still low after the engine is started, a suitableenriched fuel-air mixture must be supplied and furthermore the throttlevalve must be maintained in a position more widely opened than thenormal idling position so as to maintain the rate of idling rotation ofthe engine at a suitably high value for obtaining a stable rotation ofthe engine and quickly bringing the engine to the normal operationtemperature. However, as is well known, the throttle valve is generallyconnected to the accelerator pedal and biased by a return spring so thatit will quickly return to the idling position when the accelerator pedalis not acturated. Therefore, with only the force of the bimetal, it isimpossible to mechanically vary the degree of opening of the throttlevalve against the biasing force of the return spring. In order to solvethis problem, there has been proposed an arrangement in which a steppedcam is provided for engagement with a lug of a lever integral with thethrottle valve so as to prevent the biasing force of the return springfrom being imposed on the bimetal and thereby to hold the throttlefuel-air in one of the stepped open positions when the accelerator pedalis released, without allowing said valve to return to the idlingposition. However, such an arrangement still suffers the disadvantagesthat the step of the cam to be engaged under the force of the bimetalmust be determined while the accelerator pedal is actuated, namely whilethe return spring is not acting on the throttle valve, and the positionof the throttle valve must be regulated stepwise within the number ofsteps of said cam, which requires a cumbersome operation of theaccelerator pedal, and that a special cam as mentioned above can only beusable. It has had the additional disadvantage that, when the engine isleft running without actuating the accelerator pedal, it continues torotate with the throttle valve being held in the position correspondingto the engine temperature at the first time of start, so that thehorsepower to be consumed by friction decreases with the cooling watertemperature and oil temperature of the engine elevating, with the resultthat the rate of idling rotation of the engine rises gradually andfinally the the engine is stopped due to unduly high fuel concentrationof the fuel-air mixture.

SUMMARY OF THE INVENTION The first object of the present invention,therefore, is to provide a carburetor in which the degree of opening ofa throttle valve can be continuously adjusted according to the enginetemperature without actuating an accelerator pedal, so as to eliminatethe abovedescribed disadvantages.

The second object of the invention is to provide a carburetor in which adetector element producing a large operating force is used as enginetemperature detecting means, and said temperature detecting means ismechanically connected by means of a cable to a fast idle cam whichcontrols the degrees of opening of a choke valve and a throttle valve,whereby said temperature detecting means can be mounted in an optionalposition of the engine.

The third object of the invention is to provide a carburetor which isprovided with a mechanism by which a choke valve is opened inassociation with the opening motion of a throttle valve when there hasarisen the necessity of operating the engine with the throttle valvefully opened while the engine is not yet heated to a high temperature.

According to the present invention there is provided a carburetorcomprising temperature detecting means having a portion being movableaccording to a temperature change of an engine, a main body, a fast idlecam fixed to said main body, a cable connecting the movable portion ofsaid temperature detecting means with said fast idle cam to displace thelatter according to the movement of said movable portion, a choke valveoperatively connected to said fast idle cam, a throttle valve mounted insaid main body and a link work which be forcibly brought into engagementwith said fast idle cam and transmit the displacement of said cam tosaid throttle valve to open and close the latter, said throttle valvemoving in an opening direction when said choke valve moves in a closingdirection and vice versa.

These and other objects, features and advantages of the presentinventionwill be understood in greater detail from the followingdescription and the associated drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatical view showing theessential portion of an embodiment of the carburetor according to thepresent invention;

FIG. 2 is a side view of a portion of the carburetor looking in thedirection of the arrow II in FIG. 1;

FIG. 3 is a vertical sectional view showing one form of temperaturedetecting means used in the carburetor of the invention; and

FIG. 4 is a diagrammatical view illustrating the operation of a portionof the carburetor of FIG. 1 and showing how the choke valve is opened inassociation with the throttle valve when said throttle valve is fullyopened upon actuation of an accelerator pedal.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will bedescribed hereunder with reference to an embodiment shown in theaccompanying drawings. Referring to FIGS. 1 and 2, refer ence numeral 1designated a main body of the carburetor but the portions, e.g., a floatchamber, etc., which are of no significance to the present invention areomitted. Reference numeral 2 designates a temperature detector and 3designates a cable mechanically connecting said temperature detector 2with a fast idle cam 8 mounted on the main body 1 of the carburetor andhaving a core wire 4 slidably extended therein. Reference numeral 5designates a member by which the cable 3 is secured to the main body 1of the carburetor. The core wire 4 is extended beyond the member 5 andconnected to the fast idle cam 8 by means of a stud 6. The fast idle cam8 is composed of a lever portion 8' and a cam portion 8", and the corewire 4 is tightened to the stud 6 by a screw 7. The stud 6 is rotatablymounted on the lever portion 8 of the fast idle cam 8. On a pin 10 arefixedly mounted a lever 9 and a choke valve 11. The choke valve 11 andthe lever 9 are rotatable about the pin 10 inside and outside of themain body 1 respectively. In FIG. 1, the choke valve 1 1 is shown in itsfully closed position. The lever 9 and the fast idle cam 8 are connectedwith each other by means of a torsion spring 12 in such a manner thatthe lever 9 rotates integrally with the cam 8 when said cam 8 is rotatedwhether in a clockwise direction or a counterclockwise direction but thecam 8 does not rotate with the lever 9 when said lever 9 is rotated in acounterclockwise direction. A lever 14 and a lever 15 are fixedintegrally with each other by welding or other means and rotatablymounted on a pin 13 fixed on the main body 1 of the carburetor. Thelever 15 has a lug 15 integrally formed therewith. The lever 14 isconnected by means of a rod 16 to a lever 17 which is fixedly mounted ona pin 18 on which a throttle valve 19 is fixedly mounted. A rotation ofthe lever 14 is transmitted through the rod 16 to the lever 17 to rotatethe same. Thus, the linkage consisting of the levers 14, 15, and rod 16and the lever 17 plays the role of adjusting the degree of opening ofthe throttle valve 19 according to the rotation of the fast idle cam 8,in cooperation with the cam surface of the cam portion 8 of said cam.Reference numeral-20 designates a lever for externally operating thethrottle valve 19, which is connected to an accelerator pedal not shown.Reference numeral 23 designates a stop bolt for adjusting the normalposition of the throttle valve 19. A spring 21 is a return spring forthe fast idle cam 8 and extended between the lever portion 8' of saidcam and a spring holding arm 22. An example of the practicalconstruction of the temperature detector 2 will be described withreference to FIG. 3. An end 24 of the cable 3 is secured to a retainerplate 26 which in turn is secured to an end of a main body 25 of thetemperature detector. One side of the retainer plate 26 constitutes aspring bearing surface to bear a spring 27. The main body 25 of thetemperature detector has a mounting flange 25 and securely holds adetector element 30. The detector element is of the type in which a pin31 is moved in and out of a casing by taking advantage of thermalexpansion and contraction of a solid or liquid, e.g., wax, due totemperature change. The pin 31 receives the spring load of the spring 27through a spring seat 28 and a receiving plate 29, and in an end portion28' of said spring seat 28 is secured an enlarged diameter end 4 of thecore wire 4 extending in the cable 3. Since the detector element 30utilizes the thermal expansion and contraction of a solid or liquid asstated above, it can easily generate a sufficiently large force, e.g., aforce of IO to 100 kgs. Therefore, the force of the spring 27 can bemade sufficiently stronger than that of the spring 21 even when saidspring 21 has a force sufficient to operate the throttle valve 19 or aforce stronger than that of a return spring for the accelerator pedal.

Now, the operation of the carburetor of the invention constructed asdescribed above will be described hereunder. When the temperaturedetector 2 is mounted in an optional position where the enginetemperature can be detected, e.g., on an exhaust pipe, the pin 31 of thedetector element 30 when the engine temperature is low is in arelatively retracted position and hence the spring 27 is in a relativelystretched position. Since the spring 27 is designed to be sufficientlystrong, the core wire 4 is pulled by said spring in the direction of thearrow a against the biasing force of the spring 21 so that the fast idlecam 8 is rotated in a clockwise direction to close the choke valve 1 l.The rotation of the fast idle cam 8 also causes the lever 15, which isforcibly held in engagement with the cam surface of the cam portion 8"of said cam under the biasing force of the return spring (not shown) forthe accelerator pedal connected to the lever 20, to rotate clockwise byan amount as determined by the'configuration of said cam surface. Thismotion of the lever 15 is transmitted through the rod 16 to the lever 17and said lever 17 causes the throttle valve 19 to rotate in thedirection of the arrow b or in an opening direction through pin 18.Thus, it will be understood that, by suitably selecting theconfiguration of the cam surface of the cam portion 8", the throttlevalve 19 can be opened to a degree greater than the degree of openingduring the normal idling rotation of the engine by an amount c shown inFIG. 1. As the engine temperature gradually rises, the pin 31 of thetemperature detector element 30 projects more and more accordingly andtherefore, the spring 27 is compressed by an amount corresponding to theamount of projection of the pin 31. As a result, the core Wire 4 in thecable 3 is pulled by the spring 21 in a direction opposite to thedirection of the arrow a and accordingly the fast idle cam 8 is rotatedin a counterclockwise direction to slightly open the choke valve 11. Thelever 15 in engagement with the cam surface of the cam portion 8" isrotated in a counterclockwise direction and the rotation of said lever15 is transmitted through the linkage to the throttle valve 19, causingsaid throttle valve to rotate in a closing direction. Thus, the throttlevalve 19 takes a new open position corresponding to the degree ofopening of the choke valve 11. It will be understood, therefore, that bysuitably selecting the configuration of the cam surface of the camportion 8", the amount c shown in FIG. 1 can be continuously varied asdesired according to the engine temperature. There is an occasionwherein the engine is operated with the throttle valve fully opened evenbefore the engine is sufficiently heated. On such an occasion, itbecomes necessary to open the choke valve 11 to a suitable degree ofopening. The operation to achieve this will be explained with referenceto FIG. 4. When the throttle valve 19 is fully opened by rotating thelever 20 in a clockwise direction, the lever 17 causes the levers 14, 15to rotate in a clockwise direction about the pin 13 through the rod 16.By this rotation, one end of the lever 15 rotates in a direction to moveaway from the cam portion 8" of the cam 8 to take a position notinterfering with the rotation of the cam 8 and the lug 15 at the otherend thereof is brought into engagement with the lever 9 causing saidlever to rotate in a counterclockwise direc tion, whereby the chokevalve 11 is opened against the biasing force of the torsion spring 12which operatively connects said lever 9 with the cam 8.

In the present invention, since the temperature detector 2 comprises thedetector element 30 which utilizes the principle of liquid expansion orthe like and can generate a large force as described above, it becomespossible to mechanically connect said temperature detector 2 and thefast idle cam 8 to each other by means of the cable 3 and therefore, tomount said temperature detector 2 in an optional position where theengine temperature can be detected. Furthermore, since the large forcegenerated by the expansion of the detector element 30 is transmittedthrough the cable 3 to the fast idle cam 8 by which the choke valve 11in the main body 1 of the carburetor is opened and closed, to adjust thedegree of opening of said choke valve 11 and the degree of opening ofthe throttle valve 19 in said main body 1 is adjusted according to thedisplacement of said cam 8, the degree of opening of said throttle valve19 can be automatically adjusted according to the engine temperaturewithout requiring actuation of the accelerator pedal. Still further,according to the present invention the characteristic of adjusting thedegree of opening of the throttle valve can be continuously varied tomeet a variety of demands by suitably selecting the configuration of thecam surface of the cam 8.

We claim:

1. In an engine a carburetor having choke and throttle valves comprisinga first lever fixed to a shaft to which said choke valve is affixed,said lever being rotatable to operate said choke valve in accordancewith the operation of said throttle valve when said engine is cold, afast idle cam rotatably mounted on said shaft, said cam having a cambearing surface, and said cam being adapted to rotate in accordance withthe temperature of said engine to operate said throttle valve, a

spring extending between said fast idle cam and the housing of saidcarburetor, said spring providing a choke valve opening and throttlevalve closing force when the engine temperature rises, a torsion springdisposed between said lever and said fast idle cam and connecting saidlever and said fast idle cam to one another, a second lever engagingsaid first lever and said fast idle cam, a third lever fixedly securedto said second lever, said second lever having a lug portion whichrotates said first lever to open said choke valve as said throttle valveopens when said engine is cold, a rod disposed between said third leverand a fourth lever fixed to said throttle valve for interlocking saidsecond lever with said throttle valve, a temperature detector having avolume which changes according to engine temperature, said temperaturedetector including a pin which moves with respect to the housing of saiddetector in accordance with the temperature of said engine and a cabledisposed between said temperature detector and said fast idle cam totransmit the displacement of said pin of said temperature detector tosaid fast idle cam, said cable enabling the housing of said carburetorand said temperature detector to be independent of each other andenabling said temperature detector to be disposed at any location whereit is possible to detect engine temperature.

1. In an engine a carburetor having choke and throttle valves comprisinga first lever fixed to a shaft to which said choke valve is affixed,said lever being rotatable to operate said choke valve in accordancewith the operation of said throttle valve when said engine is cold, afast idle cam rotatably mounted on said shaft, said cam having a cambearing surface, and said cam being adapted to rotate in accordance withthe temperature of said engine to operate said throttle valve, a springextending between said fast idle cam and the housing of said carburetor,said spring providing a choke valve opening and throttle valve closingforce when the engine temperature rises, a torsion spring disposedbetween said lever and said fast idle cam and connecting said lever andsaid fast idle cam to one another, a second lever engaging said firstlever and said fast idle cam, a third lever fixedly secured to saidsecond lever, said second lever having a lug portion which rotates saidfirst lever to open said choke valve as said throttle valve opens whensaid engine is cold, a rod disposed between said third lever and afourth lever fixed to said throttle valve for interlocking said secondlever with said throttle valve, a temperature detector having a volumewhich changes according to engine temperature, said temperature detectorincluding a pin which moves with respect to the housing of said detectorin accordance with the temperature of said engine and a cable disposedbetween said temperature detector and said fast idle cam to transmit thedisplacement of said pin of said temperature detector to said fast idlecam, said cable enabling the housing of said carburetor and saidtemperature detector to be independent of each other and enabling saidtemperature detector to be disposed at any location where it is possibleto detect engine temperature.